I have a 2003 Trailblazer LS, 4.2L - 6 cylinder. 191,000+ miles. It has been running rough for a while but just off and on until last Monday. It sounded just awful and was really shaking. My check engine light has been on but started blinking rapidly at me. I took it to have it read and I got the following codes c0237, p0440, and p1345. Changed the fuel filter (it was time to change) and the crankshaft position sensor. Still running crappy and throwing 5 different codes (didn't write them down). Today I changed the spark plugs, they looked fouled and had rust lookin' stuff on the bottom end, I also noticed oil coming from the timing solenoid area so I pulled it and it was gunked up, replaced it as well. Still a no go. It ran a lil' better but still shaking. The check light would come on and blink and go back off so I drove it a little longer still no light, then turned on the air and there it went. Came on and started blinking at me. Took it to have the codes pulled and I only got one p0301 misfire #1. I'm thinking it is just a bad ignition coil in #1 but I'm tired of throwing money at it. Any other ideas than just the coil? Also I had a complete fuel system flush done in Feb. last year. I changed the plugs at that time too.

well you have done a lot of stuff yourself so try this: take the coil and plug out of cylinder#1 and switch it with the ones in next cylinder over. Drive the car and see if the code moves over to the other cylinder. If it does then yes you probably have a bad coil. If it still stays on #1 you need to look at fuel or a mechanical problem with #1 cylinder.

the only code there that would probably cause an engine problem would be your cam and crank correlation. You should do some checking on your cam sensor. also verify that your crank pulley bolt is tight. (has the crank pulley been taken off recently?)

If there was a big evep problem it could be a problem too, but not usually.